Clean up get() calls, remove commented out code

@Ignat99 PTAL.

As suggested by @dionyziz at https://github.com/OpenBazaar/OpenBazaar/pull/658#issuecomment-56653243 I created a PR out of my own code-review comments.
I regret to say I am against that change. The problem is, this will break code that explicitly tests for `None` in the absent fields. Our test coverage not being that great, I do not know whether there is such code at the moment. Please retract that particular change for now.